mybatis自动填充时间字段

对于实体中的created_on和updated_on来说，它没有必要被开发人员去干预，因为它已经足够说明使用场景了，即在插入数据和更新数据时，记录当前时间，这对于mybatis来说，通过拦截器是可以实现的，记得之前说过在jpa中实现的方法，主要通过jpa的注解实现的，因为今天的mybatis需要用到java的拦截器。

定义两个注解

@retention(retentionpolicy.runtime)
@target( {elementtype.field})
public @interface createdonfuncation {

  string value() default "";
}
@retention(retentionpolicy.runtime)
@target( {elementtype.field})
public @interface updatedonfuncation {

  string value() default "";
}

使用这两个注解

@getter
@builder(tobuilder = true)
@tostring
public class userinfo {
  private long id;
  private string name;
  private string email;

  @createdonfuncation
  private localdatetime createdon;
  @updatedonfuncation
  private localdatetime updatedon;
}

定义拦截器，重写赋值的语句

package com.lind.basic.mybatis;

import com.baomidou.mybatisplus.extension.handlers.abstractsqlparserhandler;
import java.lang.reflect.field;
import java.time.localdatetime;
import java.util.properties;
import lombok.data;
import lombok.equalsandhashcode;
import lombok.experimental.accessors;
import org.apache.ibatis.logging.log;
import org.apache.ibatis.logging.logfactory;
import org.apache.ibatis.mapping.mappedstatement;
import org.apache.ibatis.mapping.sqlcommandtype;
import org.apache.ibatis.plugin.interceptor;
import org.apache.ibatis.plugin.intercepts;
import org.apache.ibatis.plugin.invocation;
import org.apache.ibatis.plugin.plugin;
import org.apache.ibatis.plugin.signature;

/**
 * 时间拦截器.
 */
@equalsandhashcode(callsuper = true)
@data
@accessors(chain = true)
@intercepts( {
    @signature(
        type = org.apache.ibatis.executor.executor.class,
        method = "update",
        args = {mappedstatement.class, object.class})})
public class createupdatetimeinterceptor extends abstractsqlparserhandler implements interceptor {

  private static final log logger = logfactory.getlog(com.baomidou.mybatisplus.extension.plugins.sqlexplaininterceptor.class);

  private properties properties;

  @override
  public object intercept(invocation invocation) throws throwable {
    mappedstatement mappedstatement = (mappedstatement) invocation.getargs()[0];

    // 获取 sql 命令
    sqlcommandtype sqlcommandtype = mappedstatement.getsqlcommandtype();

    // 获取参数
    object parameter = invocation.getargs()[1];

    // 获取私有成员变量
    field[] declaredfields = parameter.getclass().getdeclaredfields();

    for (field field : declaredfields) {
      if (field.getannotation(createdonfuncation.class) != null) {
        if (sqlcommandtype.insert.equals(sqlcommandtype)) { // insert 语句插入 createtime
          field.setaccessible(true);
          field.set(parameter, localdatetime.now());
        }
      }

      if (field.getannotation(updatedonfuncation.class) != null) { // insert 或 update 语句插入 updatetime
        if (sqlcommandtype.insert.equals(sqlcommandtype) || sqlcommandtype.update.equals(sqlcommandtype)) {
          field.setaccessible(true);
          field.set(parameter, localdatetime.now());
        }
      }
    }

    return invocation.proceed();
  }

  @override
  public object plugin(object target) {
    if (target instanceof org.apache.ibatis.executor.executor) {
      return plugin.wrap(target, this);
    }
    return target;
  }

  @override
  public void setproperties(properties prop) {
    this.properties = prop;
  }
}

添加测试用例

  @test
  public void insert() {
    userinfo userinfo = userinfo.builder()
        .name("lind")
        .email("[e-mail]")
        .build();
    userinfomapper.insert(userinfo);
    system.out.println("userinfo:" + userinfo.tostring());
  }

解决是我们所预想的，created_on和updated_on被自动赋上值了。

userinfo:userinfo
(
id=1085780948955959297, 
name=lind, 
email=[e-mail], 
createdon=2019-01-17t14:08:45.665,
updatedon=2019-01-17t14:08:45.665
)